As disclosed in U.S. Pat. No. 3,728,132 (Sugimoto et al.), glycosylsucrose or sucrose-coupled starch syrup is a sweetener, obtained by subjecting a mixture solution of a liquefied starch and sucrose to the enzymatic action of a bacterial cyclodextrin glycosyltransferase (EC 2.4.1.19) to transfer some glucose moieties from the liquefied starch to the glucose residue of the sucrose molecule in .alpha.-1,4-fashion. Glycosylsucrose is available in large quantity as "Coupling Sugar", Registered Trade Mark of Hayashibara Co., Ltd., Okayama, Japan.
One advantage of glycosylsucrose is the feasibility as a low-cariogenic sweetener because it does not form cariogenic water-insoluble glucan and forms substantially no organic acid.
In order to make the most of the low-cariogenicity, it is necessary to avoid the breakdown of glycosylsucrose in the production and storage of processed food products wherein glycosylsucrose is used.
Since pectin jelly is suitable for mass production because of the fact that it is, unlike agar jelly, storable under freezing conditions, its production has been steadily increased.
It is, however, very difficult to produce a pectin jelly having a satisfactory gel strength while stably maintaining glycosylsucrose because the production steps of pectin jelly involves acidic, high-temperture and pressure conditions which are severe on glycosylsucrose.
Kagaku to Seibutsu, Vol.7, No.3, pp. 142-143 (1969), reports that the mechanism of gel formation with high methoxyl pectin, a pectin with a methoxyl content exceeding 7%, is entirely different from that with low methoxyl pectin, a pectin having a methoxyl content of below 7%. "High- and low methoxyl pectins" are abbreviated hereinafter as "HMP" and "LMP" respectively. According to the article, pectin jelly with HMP is a hydrogen-bonded type gel by HMP-saccharide-acid-water system, and the optimum pH for gel formation is in the range of 2.8-3.2; and, in contrast, pectin jelly with LMP is an ionically-bonded type gel by LMP-multivalent metal ion-water system, and the presence of saccharide or acid is not necessarily required. Also is reported that the use of saccharide and/or acid is necessary to improve the flavor of pectin jelly, which complicates the mechanism of gel formation with LMP.
Additionally, Journal of Japanese Society of Nutrition and Food Science, Vol. 28, No. 1, pp. 17-24 (1975), reports that LMP has a relatively wide setting pH range, and that the gel formation occurs at a pH in the range of 2.5-6.5.
Thus, there existed strong needs for a process to produce a glycosylsucrose-containing pectin jelly having a satisfactory gel strength while avoiding the breakdown of the glycosylsucrose constituent. It will be apparent from the followings that the present invention does satisfy these needs.